The cable generally comprises a core made up of electrical and/or optical conductors allowing energy and information to be transmitted between sonar equipment situated onboard the ship and the antennas. The core of the cable is generally covered by strands of metal wires which provide the mechanical strength of the cable. The makeup of the cable dictates a minimum radius of curvature thereof. Below this radius, inadmissible mechanical stresses are induced and cause these elements to deteriorate. The winch fixed to the deck of the ship has a drum onto which the cable can be wound when the sonar is inactive and when the antennas are stowed onboard the ship. The diameter of the drum guarantees that the wound elements will not be curved to a radius smaller than the minimum radius of curvature.
When the towed elements are in the sea, the cable is guided by the fairlead which safeguards its effective radius of curvature. During towing, the ship may alter its speed and its heading. Other involuntary movements of the ship may occur when the sea state worsens, notably in heavy weather. These movements of the ship lead to a change in the direction of the cable with respect to the axis of the ship. In order to prevent changes in direction from damaging the cable, the fairlead may be fixed with respect to the ship and have a flared trumpet shape opening toward the rear of the ship.
Furthermore, in underwater acoustics, the fairlead needs to be suited to allowing the antennas to be raised up onto the deck of the ship. The fairlead is, for example, open at its top. The ship may be equipped with an articulated arm that allows the fish to be passed over the fairlead.
The existing devices are bulky and require an actuator to move the articulated arm. In addition, as the fish is being passed over the fairlead, anti-unrigging systems need to be employed to prevent the cable to which the towed elements are fixed from leaving its housing in the fairlead.